Scientists from the Max Planck Institute for Brain Research and the Okinawa Institute of Science and Technology have studied camouflage in the common cuttlefish (Sepia officinalis) — a master of camouflage — as behavioral motion towards background matching in skin-pattern space. Their observations suggest that the cuttlefish’s camouflage system is highly flexible and adaptable, providing new insights into this complex physiological process.
The common cuttlefish (Sepia officinalis). Image credit: Stephan Junek, Max Planck Institute for Brain Research.
“Cephalopod camouflage consists of matching the animal’s appearance to that of its substrate and typically contains 2D and 3D components,” said senior author Dr. Gilles Laurent from the Max Planck Institute for Brain Research and colleagues.
“Although both components are technically textural in this field the term ‘texture’ is often applied only to 3D features, caused, for example, by the contraction of skin papillae.”
“We studied the 2D features of camouflage and therefore refer to them as skin patterns and to the process as pattern matching,” they added.
“Pattern matching does not consist of a faithful reproduction of the substrate’s appearance but, rather, of the visually initiated statistical estimation and generation of that appearance.”
“These sophisticated operations are carried out instinctively by the brain of animals that diverged from us more than 550 million years ago, well before large brains existed.”
“The generation of 2D skin patterns relies on a motor system that controls the expansion state of up to several million pigment cells (chromatophores) embedded in the animal’s skin, among other specialized cell types.”
“The expansion state of each chromatophore depends on a radial array of muscles controlling the size of a central pigment sac and, therefore, on the activity of one to a few motoneurons, the dendrites and somata of which lie in the animal’s central brain.”
“The generation of a skin pattern therefore results from the appropriate coordination and control of tens of thousands of motoneurons by a system that interprets complex visual scenes.”
In their research, the authors studied camouflage behavior in the common cuttlefish over natural and artificial backgrounds, gathering over 200,000 images that were used to map the color-change process at a single-cell resolution.
The data from these maps indicated that each pattern was highly detailed and that the same background could yield a multitude of different outcomes.
These pathways to camouflage were found to involve a form of continuous feedback and the final camouflage was the product of successive error-correction steps, which indicates that the process is highly adaptable and does not follow a set path each time.
The exception to this rule was during blanching, a defense mechanism in which cephalopods turn pale in response to threatening stimuli.
This process was observed to be rapid and direct, and memory retained of the initial camouflage was expressed again once the threat was withdrawn.
The team’s results provide valuable insight into the way that these survival mechanisms interact with one another, and how the complex process of color-matching is achieved at a cellular level.
“Unlike camouflaging, blanching was fast and direct, suggesting it uses a different and repeatable control system,” said co-author Dr. Dominic Evans, a postdoctoral fellow at the Max Planck Institute for Brain Research.
“The cuttlefish would often overshoot their target skin pattern, pause, and then come back,” said first author Theodosia Woo, a graduate student at the Max Planck Institute for Brain Research.
“In other words, cuttlefish don’t simply detect the background and go straight to a set pattern, instead, it is likely that they continuously receive feedback about their skin pattern and use it to adjust their camouflage.”
“Exactly how they receive that feedback — whether they use their eyes, or whether they have a sense of how contracted the muscles around each chromatophore are — we don’t yet know.”
The study was published in the journal Nature.
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T. Woo et al. The dynamics of pattern matching in camouflaging cuttlefish. Nature, published online June 28, 2023; doi: 10.1038/s41586-023-06259-2
